Keywords: structural health monitoring, flexible retaining wall, finite element, back-analysis, embedded sensors, model refinement.

Over the last fifty years, earthquake engineers have relied on data from laboratory experiments and from post-earthquake reconnaissance efforts to gain knowledge and confidence in numerical analyses and design procedures. The scarcity of reconnaissance data and the need for elucidating the response mechanism associated with actual structures make full-scale and near full-scale experimentation more and more relevant. The need to improve the knowledge about the seismic behaviour of geotechnical structures was the main motivation to design and setting up of a full-scale monitoring system for a flexible retaining wall that is a part of the new Student House at University of Molise [1].

The monitoring system consists of six custom made sensor modules embedded into two nearby piles. Each module allows acceleration measurements along the horizontal (normal to the wall plane) and the vertical direction. Specific requirements were established to minimize changes in stiffness and strength due to the presence of the sensors [2]. With this aim additional reinforcement has been designed.

The structural health monitoring (SHM) system is going to be completed with installation of a number of sensors on the nearby building under construction on the excavated side of the wall. Studies on the complete interaction between soil, geotechnical structures and building structures will be then attempted at the end of the construction of the Student House.

Static and dynamic measurements are periodically collected. Preliminary results of back-analyses from static measurements by embedded inclinometers have been described. The experimental results have shown a final horizontal displacement for the wall around 80 mm. The final configuration has been reached after five months since the excavation phase. Results of static measurements have been used for the calibration of a numerical model. Input data concerning the soil characteristics have been obtained from geotechnical investigations.

The retaining wall has been modelled as an equivalent linear elastic plate. The horizontal displacements obtained from numerical analyses have been compared with the inclinometer measurements, obtaining a good agreement between experimental and numerical data. Further studies are in progress concerning the dynamic behaviour of the wall.

1

G. Fabbrocino, C. Laorenza, C. Rainieri, F. Santucci de Magistris, "Seismic monitoring of structural and geotechnical integrated systems", Proceedings of the 2nd Asia-Pacific Workshop on Structural Health Monitoring, Melbourne, Australia, 2008.

2

G. Fabbrocino, C. Laorenza, C. Rainieri, F. Santucci De Magistris, C. Visone, "Structural and geotechnical seismic monitoring of the new Student House in Campobasso, Italy", Proceeding of the International Conference on Performance-Based Design in Earthquake Geotechnical Engineering - from case history to practice, Tsukuba, Japan, 2009.

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